Battery Management System Using Open Circuit Voltage for Degradation Diagnosis
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Solution Overview
Problem
Accurately and efficiently determining the mechanisms of lithium ion battery cell degradation is challenging due to complex cycling and storage conditions, requiring invasive and time-consuming tests, which can damage the battery and provide insufficient information for detailed fading mechanisms.
Innovation Solution
A battery management system that uses data fitting techniques on half-cell and full-cell open circuit voltages to determine anode and cathode stoichiometry bounds, measuring cell open circuit voltage at various states of charge, and identifying changes in stoichiometry to determine the total cyclable lithium ion and active material loss, thereby generating a battery health indicator to manage power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If invasive tests are used to determine battery degradation mechanisms, then measurement precision is improved, but the battery reliability deteriorates due to damage
Solution Approach 1:
The patent replaces invasive physical tests with electrochemical measurements and mathematical modeling. By using open circuit voltage measurements combined with data fitting techniques to determine stoichiometry bounds and identify degradation mechanisms, the system achieves accurate diagnosis without mechanical or chemical intrusion that would damage the battery.
Solution Approach 2:
The patent introduces intermediate measurement parameters (open circuit voltage at multiple states of charge) and mathematical models (data fitting techniques, stoichiometry calculations) as mediators between the battery and the degradation analysis. This indirect approach allows accurate mechanism identification without direct invasive testing.
2Loss of information
If traditional testing methods are used to analyze battery degradation, then degradation mechanisms can be identified, but loss of time occurs due to test duration
Solution Approach 1:
The patent measures open circuit voltage at a selected plurality of states of charge (rather than continuous measurement across the entire range) to identify degradation mechanisms. This partial sampling approach, combined with data fitting techniques, provides sufficient information to determine stoichiometry bounds and degradation modes without requiring exhaustive testing.
Solution Approach 2:
The patent performs preliminary rest periods before voltage measurements to ensure stable open circuit voltage readings. This preliminary action eliminates the need for prolonged continuous testing, as the rest-period stabilization allows accurate voltage capture that can then be used for degradation analysis.
3Measurement precision
If complex cycling and storage conditions are considered in battery testing, then degradation accuracy is improved, but device complexity increases
Solution Approach 1:
The patent changes the parameters being measured from complex multi-dimensional degradation metrics to specific electrochemical parameters (open circuit voltage at different states of charge, stoichiometry bounds). By focusing on these fundamental parameters and using data fitting techniques, the system accurately characterizes degradation under complex cycling and storage conditions without requiring complex testing apparatus.
Data Source
AI summary
Systems and methods to manage battery cell degradation are provided. The system determines anode stoichiometry bounds in full-cell and cathode stoichiometry bounds in full-cell. The system measures a cell open circuit voltage subsequent to a rest duration. The system identifies, via a data fitting technique and the cell open circuit voltage, a change in the anode stoichiometry bounds in full-cell and a change in the cathode stoichiometry bounds in full-cell. The system determines a total cyclable lithium ion for the battery cell, an amount of anode active material and an amount of anode cathode material. The system determines a primary capacity fade mechanism for the battery cell. The system generates a battery health indicator, selects a command, and provides the command to manage power consumption from the battery cell.